This is a simple application to draw four arcs or other custom patterns on corners. This application requires only permission for reading custom images, and uses almost no resource.
By default it draws four round corners, but you may customize preferred patterns by putting a file under Pictures/org.gemini.round_corner/. File name and position mapping:
0.0.png - top left.
90.0.png - top right.
180.0.png - bottom right.
270.0.png - bottom left.
a.png - all four corners.
Other file extensions are also supported, say, jpg, jpeg, bmp.

You can fine some samples at https://github.com/Hzj-jie/android-round-corner/tree/master/samples. Copying you preferred ones, putting them in the expected folder, and renaming them, all done.

This application does not automatically execute itself on boot: I use https://play.google.com/store/apps/details?id=org.gemini.init to do it. You may find a sample at https://github.com/Hzj-jie/android-init/blob/master/sample/init.sh.

I do not think this simple functionality deserves a cent, so I wrote one myself. You may get the source code at https://github.com/hzj-jie/android-round-corner.